The infestation of companion animals and/or their environment, and in particular household pets such as dogs and cats, with ectoparasitic arthropods such as fleas, ticks and the like, which live by hematophagy (i.e., by sucking the animal's blood), is highly undesirable. The prior art has developed numerous ready-to-use topical formulations and compositions for treating such infestations, many of which are “spot on” or “pour on” formulations that are applied by deposition on the animal's skin.
Such topical applications can be desirable since many formulations are acceptably safe when used topically, even if not when used internally. Topical applications can be more advantageous, however, if the amount of liquid applied to the animal can be minimized. This should be balanced with the need for appropriate dosage to achieve the desired pesticidal effect. Therefore, it is desirable to use highly active insecticides so that the total volume of the insecticide applied to the animal can be minimized.
Topical applications often contain an active component which is an insect growth regulator (“IGR”). IGRs kill immature insects by interfering with the insect's development from the egg and larval stages into adulthood in one or more ways. In general, some IGRs cause the insect to develop too rapidly, while others slow down that development or prevent it from taking place at all. More particularly, IGRs can mimic or disrupt the natural hormones involved in molting and/or exoskeleton formation during arthropod growth while in its immature stages, or they mimic or disrupt the natural juvenile hormones which have an impact on the maturing processes leading to the transition (metamorphosis) of an arthropod from an immature stage to a later immature stage or to the adult stage.
Within these broader categories, IGRs can be further sub-divided into classes, depending upon their mode of action. For example, some IGRs are the natural hormone itself or synthetically created versions thereof, but because they duplicate the effect of the natural hormone, the administration of such IGRs provides an “overdose” which negatively impacts the developmental cycle of the arthropod. Other IGRs act on the natural hormone directly, either interfering with its production or inhibiting its activity, such that the developmental cycle of the arthropod is negatively affected. Still other IGRs can emulate the natural hormones such that they bind to cell surface receptor sites for that hormone, thus acting as agonists or antagonists and preventing the natural hormone from triggering its normal cellular response, thereby also negatively impacting the arthropod's developmental cycle.
It is known that an IGR can have a significant effect on the development of an arthropod, even when used at an extremely low level. It is also known that a combination of two IGRs in the same topical formulation, applied to the same animal so as to be present at the same time, can have an enhanced synergistic effect, rather than the expected, merely additive effect of the two individual IGRs when each is acting alone. However, this synergistic effect was previously thought to be limited to a topical formulation containing two IGRs from the same particular class, specifically, from the class of juvenile hormone mimics. Moreover, this synergistic effect has been found in the situation in which one of the IGRs was a “mobile” (volatile) IGR, that is, an IGR existing as a liquid at room temperature and at atmospheric pressure, and capable of translocation in the environment (examples are methoprene and hydroprene), while the other IGR was a “non-mobile” IGR, that is, an IGR existing in solid form at room temperature and at atmospheric pressure, and which is not capable of translocation within the environment (an example is pyriproxyfen, commercially available under the trademark Nylar™).
It is now believed that a synergistic effect can be achieved with a combination of any two or more IGRs, whether they be from the same class, or from different classes, and regardless of the “mobility” or translocation capability of each. This was not previously anticipated, as many other combinations of pesticide active ingredients from the same or from similar classes of pesticides provide only an additive level of performance, and the synergistic effect mentioned in the preceding paragraph was thought to have resulted solely from the combination of a “mobile” IGR and a “non-mobile” IGR, and only when both are selected from the specific juvenile hormone mimic class of IGRs.
It is therefore the principal object of the present invention to provide ectoparasiticidal formulations for the treatment and protection of companion animals and/or their environment having enhanced efficacy.
It is another object of the present invention to provide ectoparasiticidal compositions that are easy to use.
It is yet a further object of the present invention to provide ectoparasiticidal formulations having a synergistic effect which achieves a higher level of performance than can be achieved using any of the component ingredients individually.